S93

What happens after you change a car battery? All the presets are forgotten? Is the radio still operative or does the radio act like it's been stolen and doesn't turn on?

I am about to change the battery DIY.

I am thinking how I can change it and still maintain current while I do it. I was thinking if it is possible to hook jumper cables to the new battery and carefully unhook the old battery. I would then try to connect the new battery as I release the clamps. Is this possible or am I an idiot? Ok, don't answer as it could be possible and I'm still an idiot.

Diesel Benz

I don't think it would be a bad idea to use jumper cables, except that you could use some pretty small cables if you just let the car go to sleep first, the current consumption would then be some 40 mA.

I don't think you would need to worry about the radio code on a W211 though. You would just have to normalise windows, steering, sunroof, what else? Not too bad this way either.

Gullwing

Normalize steering wheel, turn lock to lock several times.
Normalize windows and sunroof
reset clock
thats it

Davel

its very easy to change the battery in these cars. There are 2 batteries, the one in the front keeps all the settings so you should not lose any of those...

Gullwing

The battery in the front is only a back up for the sbc system. It will not power up anything else.

Barry45RPM

Do the 2007> cars (without SBC) still have that 2nd battery under the hood even though there is no longer SBC? What does that battery do then?

Diesel Benz

I've never looked at the battery from a face lift car but from the wiring diagrams it appears the "SBC battery" does not exist any more. The wiring is so much simpler on the current model when a single battery only is needed.

Gullwing

no sbc, no need for the second sbc battery.

Taylor-Made'90

It would seem that you would be able to crank your car (any car for that matter), and with the engine idling, disconnect the positive battery cable (the car should should continue running, charging off the alternator), then connect the positive cable to the new battery, then disconnect the negative cable (from old battery), slide it out of the way, slide new battery in place and connect negative cable.

The 'flow' is never interrupted....

This works in most multiple-battery setups (diesels, 12V and 24V systems).

It oughtta work here...

Diesel Benz

So why not try on your own car first? You should not compare an old diesel with hardly any electronics to a modern MB.

bertman

What about the trick of connecting a 9 volt battery through the lighter receptacal? Presumably this would maintain a small current while swapping batteries. Anyone dared try this on a MB?

Diesel Benz

The current drain would be pretty low (40 mA) if the car is in full sleep. But the cigarette lighter would not be connected at this stage. Also connecting a 9V battery in parallel with a 12 V car battery blows the small battery easily, a small 12 V lead acid or similar battery would work fine.

Davel

Nope, not correct just confirmed it powers some of the electronics in addtion to the SBC... Correct 06 and later should not have 2nd battery, i was thinking of the SL which MB continued the use of the SBC (and SLR)

Barry45RPM

'06 had SBC... '07> Do Not Have SBC

Davel

thanks

SAguirre

There is NOW WAY that I would ever try this on any W211! A 95 amp-hour battery is an integral part of the alternator and voltage regulator. The battery is used as ballast in the charging system. If there is no load the voltage could (possibly) go over 14 volts before the voltage regulator can tell the alternator to stop charging. This will FOR SURE give you a laundry list of errors and malfunctions, if you are lucky you would most likely fry some buses or computer control modules. If the alternator lets the voltage drop too much, then you will have at least 8 airbag malfunctions due to inadequate voltage. You should not change any battery on any Mercedes from the last 20 years when the engine is running.

As mentioned before, the cigarette lighter is not active when the car is in sleep mode, so putting a 9V battery in the car would also accomplish nothing.

The best idea is to use some OK cables and keep the terminals connected that way. Jumper cables are too cumbersome. If the vehicle is asleep, it should work. Also, if the cables do become unhooked, its no big deal since the car is asleep anyway and it was worth a try.

I did not think about the second battery, but I was also under the impression that it was somehow disconnected from other electronics when the car is off. Who knows?

Good luck changing the battery. My car is just about to turn 4 years old, but I am sure the battery is just over 4 years old. I guess that I have about 1 year left on it.

Steve

Vik888

Accidently killed the battery on my 08 E550 because I left the headlights in the ON position rather than AUTO and went to bed.

Roadside Assist came out to jump. What Gullwing said is correct. I also normalized the trunk.

The manual clock showed the wrong time, but picked it up from the COMAND unit and they sync'd back up after I started the car again.

All my radio stations, bluetooth pairing, memory settings for my seats, all were just fine.